RT Journal ArticleJF IEEE Transactions on Software EngineeringYR 1997VO 23IS SP 388TI An Optimal Algorithm for Scheduling Soft Aperiodic Tasks in Dynamic-Priority Preemptive SystemsA1 Alfons Crespo, A1 Ismael Ripoll, A1 Ana García-Fornes, K1 Dynamic scheduling theoryK1 hard real-timeK1 feasibility analysisK1 slack schedulingK1 soft aperiodic tasksK1 dynamic.AB <p><b>Abstract</b>—This paper addresses the problem of jointly scheduling tasks with both hard and soft real-time constraints. We present a new analysis applicable to systems scheduled using a priority preemptive dispatcher, with priorities assigned dynamically according to the EDF policy. Further, we present a new efficient on-line algorithm (the acceptor algorithm) for servicing aperiodic work load. The acceptor transforms a soft aperiodic task into a hard one by assigning a deadline. Once transformed, aperiodic tasks are handled in exactly the same way as periodic tasks with hard deadlines. The proposed algorithm is shown to be optimal in terms of providing the shortest aperiodic response time among fixed- and dynamic-priority schedulers. It always guarantees the proper execution of periodic hard tasks. The approach is composed of two parts: an off-line analysis and a run-time scheduler. The off-line algorithm runs in pseudopolynomial time <it>O</it>(<it>mn</it>), where <it>n</it> is the number of hard periodic tasks and <it>m</it> is the hyperperiod/min deadline.</p>PB IEEE Computer Society, [URL:http://www.computer.org]SN 0098-5589LA EnglishDO 10.1109/32.601081LK http://doi.ieeecomputersociety.org/10.1109/32.601081